BACKGROUND AND PURPOSE:

• Halasa et al. (CDC MMWR, 2022) assessed the effectiveness of maternal completion of a 2-dose mRNA COVID-19 vaccination series during pregnancy against COVID-19 hospitalization in infants

METHODS:

• Test-negative, case-control study
  • Real-world evaluation at 20 US pediatric hospitals during a period of Delta and Omicron variant circulation
• Participants
  • Infants aged <6 months admitted outside of their birth hospitalization to a pediatric hospital during July, 2021 to January, 2022
    • Case infants had a positive COVID-19 test
    • Control infants had a negative COVID-19 test
• Exposure
  • Maternal vaccination ≥14 days before delivery
    • Defined as completion of a 2-dose series of either Pfizer-BioNTech or Moderna mRNA COVID-19 vaccine
• Study design
  • Control-infants were matched to case-infants by site and were hospitalized within 3 to 4 weeks of a case-infant’s admission date
  • In a secondary analysis, effectiveness of maternal receipt of the second dose of COVID-19 vaccination early in pregnancy (within the first 20 weeks) and late in pregnancy (21 weeks through 14 days before delivery) was assessed
• Primary outcome
  • Vaccine effectiveness (VE) of maternal vaccination against infant COVID-19 hospitalization

RESULTS:

• Case infants: 176 | Control infants: 203
  • Median age 2 months
  • Had at least one underlying medical condition: 21%
  • Born premature (<37 weeks): 22%
• Effectiveness of maternal vaccination during pregnancy against COVID-19 hospitalization in infants aged <6 months
  • VE: 61% (95% CI, 31 to 78%)
• Effectiveness of a completed 2-dose COVID-19 vaccination series early in pregnancy (first 20 weeks)
  • VE: 32% (95% CI, –43% to 68%)
• Effectiveness of vaccine completion late in pregnancy (21 weeks through 14 days before delivery)
  • VE: 80% (95% CI, 55 to 91%)

CONCLUSION:

• Maternal COVID-19 immunization appears to provide protection to infants through passive transplacental antibody transfer
• Maternal vaccination had a VE of 61% for preventing COVID-19 hospitalization in infants
• The authors state

Overall, these findings indicate that maternal vaccination during pregnancy might help protect against COVID-19 hospitalization among infants aged <6 months

Learn More – Primary Sources:

Effectiveness of Maternal Vaccination with mRNA COVID-19 Vaccine During Pregnancy Against COVID-19–Associated Hospitalization in Infants Aged <6 Months — 17 States, July 2021–January 2022

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